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[APD] Re: Need guidance with DIY compact fluorescents

> From: "S. Hieber" <shieber at yahoo_com>
> Subject: Re: [APD] Re: Need guidance with DIY compact fluorescents

> What they are like depends on where you get them. The ones
> from AHS are made for these (13 watt) bulbs and will work
> on a few others. They are coils (sometimes called magnetic
> ballasts).
> The 15-18-20 watt ballasts are a bit diff -- made to run
> bulbs rated for higher wattage.

In general, there are three styles of ballasts. "old fashioned" starter,
rapid start and instant start. The AHS 13 watt bulbs are rapid start.

The old fashioned kind used the little silver starters to first heat the
bulb filaments. The heated filaments allow the internal arc to be stuck
with relatively lower voltages. Once the arc is struck, the starter opens
the filament circuit (or limits the current flowin through them).

Rapid start are the typical magnetic ballasts and some electronic
ballasts. They use simple internal circuitry to heat the filaments, strike
an arc then limit the current that is supplied to the bulb.

With both these types, there is always current flowing in the filaments to
keep them warm (why the ends are always very hot). This extra current uses
extra power.

Instant start ballasts are designed to supply a higher voltage across the
bulb. This allows the arc to fire without heating the filaments. In an
instant start configuration, the pair of pins on each end of the bulb are
actually shorted together! With no current flowing through the filaments,
energy is saved.

I beleive this is what the newer 32-watt T-8 bulbs are set up for. Their
pins are shorted together and therefore require an Instant Start
electronic ballast. They output about the same amount of light as a NO 40w
bulb without wasting the extra 8 watts that would keep the filaments warm.
If you tried to run them with a normal ballast, you would short out the
internals of the ballast.

I beleive that any bulb designed for starter or rapid start use can be
driven with an instant start ballast rated for the bubs wattage. I have
some linear 8 and 13 watt T-5 bulbs I use for under shelf lighting that
use instant start ballasts. They run prerty cool.


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